1. Field of the Invention
The present invention disclosed in this specification relates to a semiconductor device and a manufacturing method thereof. In particular, the present invention relates to a semiconductor device capable of transmitting and receiving data with wireless communication and a manufacturing method thereof.
2. Description of the Related Art
In recent years, a semiconductor device capable of transmitting and receiving data with wireless communication has been actively developed. Such a semiconductor device is called an IC tag, an ID tag, an RF (Radio Frequency) tag, an RFID (Radio Frequency Identification) tag, a wireless tag, an electronic tag, a wireless processor, a wireless memory, a wireless chip, or the like. Hereinafter, a semiconductor device capable of transmitting and receiving data with wireless communication may be referred to as “an RFID tag”.
An RFID tag includes an antenna and an integrated circuit (an IC chip). One of objects of an RFID tag is improvement in reliability.
In order to accomplish the improvement in reliability, there is a method of sealing both surfaces of a substrate on which components such as an IC chip, a condenser, and an antenna coil are mounted by using a sheet member (Reference 1: Japanese Patent Application Laid-Open No: 2001-63256). A distance between each surface of the substrate and the sheet member is controlled to be a constant distance by using adhesive, and thus, concavity and convexity of the components are not observed on the surface. As a result, breakdown in a portion having concavity and convexity is suppressed, and reliability of an IC card is improved.
In the above described method, adhesive is used when the substrate on which the IC chip is mounted and the sheet member are attached to each other. In other words, there is an adhesive layer between the substrate on which the IC chip is mounted and the sheet member. The adhesive layer is formed of a material having fluidity before curing and adhesion and viscosity after curing. Specifically, hot-melt adhesive or ionizing radiation (such as ultraviolet ray or electron beam)-curable adhesive is used. Such adhesive usually has a low moisture proof property. In addition, the adhesive layer is melted under conditions of a high temperature and high humidity in some cases, and there is a possibility that the mounted substrate is infiltrated from a melted portion. Therefore, it is necessary to develop a semiconductor device which is not only excellent in chemical and physical strength but also in circumstance resistance.